Hydrophobic solids and structure formation in oil sands fine tailings
- National Research Council, Ottawa, Ontario (Canada)
Hydrophobic solids, having a range of surface wettability, occur in oil sands fine tailings at both the Syncrude and Suncor plants. These relatively coarse solids appear to play a role in the stability of fine tailings by forming a structure, through inter particle flocculation, as a result of interaction with residual bitumen and naphtha. The removal of these solids, together with residual bitumen, results in a change in settling behaviour and subsequent dewatering of the tailings. A fractionation scheme has been developed that allows the hydrophobic solids to be separated selectively from both Syncrude and Suncor fine tailings samples. The solid fractions separated were characterized by particle size distribution and elemental analyses. Significant differences were found in the distribution of certain elements among the fractions as well as between Syncrude and Suncor samples. These differences are believed to be important in terms of the stability of fine tailings. Two types of solids, each having relatively high organic carbon content relative to the bulk solids, have been identified. In one case the solids were predominantly oil wettable, hydrophobic solids (HPS) while the other fraction exhibited partial hydrophobic, or biwettable, surface characteristics (BWS). Biwettable solids behave similarly to sub-bituminous coals, which flocculate in the presence of immiscible liquids of different polarity. On the other hand, HPS can form compact agglomerates after agitation with a critical amount of a water immiscible, non-polar liquid. The implication of these results is that HPS, together with BWS, could be involved in the stability of fine tailings by forming a flocculated structure through interaction of the dispersed solids with bitumen and naphtha. This flocculation can strengthen the tailings structure by reinforcing the gel networks formed by an ultra fine solids fraction also known to be resent in the tailings.
- OSTI ID:
- 229647
- Report Number(s):
- CONF-9502114--Vol.2
- Country of Publication:
- United States
- Language:
- English
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